Under physiological conditions the nose serves to actively warm up and humidify respiratory air. However, when a patient is undergoing artificial respiration, the nose is shunted by a tube or piece of hose which has one end lodged in the trachea. Thus, in such a situation the nose cannot accomplish the usual warming and humidifying functions that it normally achieves. Therefore, in such situations artificial humidification and warming of the air, which are absolutely essential for proper pulmonary function, are presently accomplished by devices based on two different principles.
Apparatus of a first type actively transfers heat and moisture to the respiratory air. The apparatus of the first type, for example, the dry, cold respiratory air is passed through an electrically heated water bath humidifier and conditioned prior to being supplied to a patient. A second type of apparatus operates passively as a heat and moisture exchanger (H.M.E.), in which case the heat and moisture are extracted from moist exhaled air at body temperature and are transferred to cold, dry air to be inhaled by a patient without actively supplying heat and moisture from the outside, that is from an external source thereof.
While it is true that state-of-the-art apparatus operating on the principle of actively supplying heat and moisture to the air is able to supply respiratory gases in a well tempered and satisfactorily humidified form, this is achieved at the expense of substantial technical complexity and requires considerable nursing attention. Consequently, the purchase price and operating costs of such apparatus are very high. On the other hand, with simple passive heat and moisture exchangers, which are of simple design and are simple to use, no such expenses are involved, although such second type of apparatus has thus far not performed satisfactorily to humidify and warm up respiratory air during artificial respiration.
There exists, therefore, the need for such a device which can perform satisfactorily and which at the same time, does not exhibit the technical complexity or require the nursing attention of state-of-the-art apparatus. The present invention fulfills such a need.